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Pollen is the male gametophyte of seed plants, which include both gymnosperms (cone-bearing plants) and angiosperms (flowering plants). Seed plants produce pollen as the male part of sexual reproduction, a process that ultimately results in the development of a seed.
In gymnosperms pollen is produced in small pollen cones (also called male cones or technically microsporangiate cones), while in angiosperms pollen is produced in anthers, which are parts of the stamens found in a flower.
Each pollen grain typically consists of one to a few cells. The wall of the pollen grain consists of two layers, the exine (outer wall) and intine (inner wall). The exine may be smooth or ornamented with spines, warts, granules, or ridges. The exine may also contain one or more openings known as apertures; these are either pores or furrows (slits), The type of aperture and the distinctive ornamentation permits the identification of the pollen grains.
Oak pollen
Ragweed pollen
Cedar pollen
Birch pollen
Pollen is primarily dispersed by animals (mainly insects) or by wind. Wind-pollinated plants are called anemophilous, while insect-pollinated plants are called entomophilous. Flowers with pollen that is dispersed by both insects and wind are called amphiphilous. It is the wind-pollinated plants that may cause the allergy symptoms in many people who are pollen-sensitive. It is estimated that about 25% to 30% of the human population have allergies with allergic rhinitis the most
When pollen is released by wind-pollinated plants, only a small percent reaches a receptive stigma or female cone. At the proper season, pollen can be so abundant that clouds of it can be seen emanating from vegetation disturbed by wind. Although much of this pollen settles close to the source, some is carried by long distances by the wind. (See Long Distance Transport).
Missouri Botanical Garden: Plants, Pollen, and Allergies
Curriculum materials for teachers and projects for students of all ages.
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